Using smartphone in China's cities,
how can I navigate by foot?
Does anyone has a creative idea if I don't read or write chinese?
Any recommended foot-navigation to China main cities? (offline maps is preferable)
You are not specifying which smartphone you have. On iOS, an excellent app is MapsWithMe, which allows you to download maps per country and sometimes per province. Major locations will be listed in English and Chinese, but lesser locations will probably only be listed in Chinese.
Since last update, Google Maps (at least in Android) allow to put map areas available offline.
Here is a review of the update: http://www.engadget.com/2012/06/27/google-maps-offline-android/